Valves are widely used in the oil and gas industry, and others, to control the flow of liquids and gases through pipelines. A typical valve includes a valve element, such as a valve plug, gate or valve ball, located inside a housing to control flow through the housing. A valve stem from the valve body exits through the housing to an exterior of the valve and is normally equipped with a handle so the valve stem can be manipulated thereby opening or closing the valve. The valve housing opens through suitable connections, such as flanges, pipe ends or the like, which are joined to a pipeline or other conduit through which gas or liquid flows.
There are some situations where it is desirable to prevent unauthorized opening or closing of a valve. The normal solution to this problem is to remove the valve handle or to place a lock out device on the valve handle. A typical situation where this is desirable is to protect a valve or equipment adjacent a valve from being stolen.
There are a variety of approaches to prevent an unauthorized person from opening or closing a valve. The earliest approach is to tie a valve wheel with a chain and padlock so it cannot be moved. More sophisticated approaches have surfaced. One such approach is to mount a rotatable cover over the valve stem which, in a one position, free wheels so no torque is applied to the valve stem upon rotation of the cover. An authorized person has a specially adapted key or wrench to selectively couple the rotatable cover to the valve stem so torque applied to the cover turns the valve stem and thereby operates the valve. It is to this class of devices that this invention most nearly relates.
Some disclosures of interest are found in U.S. Pat. Nos. 1,215,958; 4,484,595; 4,662,196; 5,071,300; 5,664,447; 5,996,613; 6,038,893; 6,089,253; 6,176,255; 6,205,826; 6,276,662; 6,543,467; 6,860,177 and 8,074,960 along with U.S. Printed Patent Applications 20030217571 and 20120126156.